U.S. Department of Commerce

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American Indian, Alaska Native, and Native Hawaiian Areas

Alaska Native Regional Corporations

Alaska Native Regional Corporations (ANRCs) were created pursuant to the Alaska Native Claims Settlement Act (ANCSA) (Pub. L. 92-203, 85 Stat. 688 (1971); 43 U.S.C. 1602 et seq. (2000)), enacted in 1971 as a ''Regional Corporation'' and organized under the laws of the State of Alaska to conduct both the for-profit and non-profit affairs of Alaska Natives within a defined region of Alaska. For the Census Bureau, ANRCs are considered legal geographic entities. Twelve ANRCs cover the entire State of Alaska except for the area within the Annette Island Reserve (a federally recognized American Indian reservation under the governmental authority of the Metlakatla Indian Community). A thirteenth ANRC represents Alaska Natives who do not live in Alaska and do not identify with any of the twelve corporations. The Census Bureau does not provide data for this thirteenth ANRC because it has no defined geographic extent and thus it does not appear in the TIGER/Line Files. The Census Bureau offers representatives of the twelve non-profit ANRCs in Alaska the opportunity to review and update the ANRC boundaries before each decennial census.



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Alaska Native Village Statistical Areas

Alaska Native Village Statistical Areas (ANVSAs) represent the more densely settled portion of Alaska Native villages (ANVs). The ANVs constitute associations, bands, clans, communities, groups, tribes, or villages recognized pursuant to the Alaska Native Claims Settlement Act of 1972 (Public Law 92-203). Because ANVs do not have boundaries that are easy to locate, the Census Bureau does not delimit ANVs. Instead, the Census Bureau presents statistical data for ANVSAs that represent the settled portion of ANVs. In addition, each ANVSA should include only an area where Alaska Natives, especially members of the defining ANV, represent a substantial proportion of the population during at least one season of the year. ANVSAs are delineated or reviewed by officials of the ANV or, if no ANV official chose to participate in the delineation process, officials of the Alaska Native Regional Corporation (ANRC) in which the ANV is located. An ANVSA may not overlap the boundary of another ANVSA, an American Indian reservation, or a tribal designated statistical area (TDSA), which are not permitted in Alaska.



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American Indian Joint Use Areas

Joint-Use Areas, as applied to any American Indian area by the Census Bureau, means an area that is administered jointly and/or claimed by two or more American Indian tribes. The Census Bureau designates legal joint-use areas as unique geographic entities for the purpose of presenting statistical data.



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American Indian Reservations and Off-Reservation Trustlands

Federal (federal AIRs) are areas that have been set aside by the United States for the use of tribes, the exterior boundaries of which are more particularly defined in the final tribal treaties, agreements, executive orders, federal statutes, secretarial orders, or judicial determinations. The Bureau of Indian Affairs maintains a list of all federally recognized tribal governments and makes final determination of the inventory federal AIRs. The Census Bureau recognizes federal reservations (and associated off-reservation trust lands) as territory over which American Indian tribes have primary governmental authority. American Indian reservations can be legally described as colonies, communities, Indian colonies, Indian communities, Indian rancheria, Indian reservations, Indian villages, pueblos, rancherias, ranches, reservations, reserves, settlements, or villages. The Census Bureau contacts representatives of American Indian tribal governments to identify the boundaries for federal reservations through its annual Boundary and Annexation Survey. Federal reservations may cross state and all other area boundaries.

State (state AIRs) are reservations established by some state governments for tribes recognized by the state. A governor-appointed state liaison provides the names and boundaries for state-recognized American Indian reservations to the Census Bureau. State reservations must be defined within a single state, but may cross county and other types of boundaries. To further identify and differentiate state-recognized American Indian areas from those that are federally recognized, the text, "(state)" is appended to the AIR name.

Off-Reservation Trust Lands are areas for which the United States holds title in trust for the benefit of a tribe (tribal trust land) or for an individual American Indian (individual trust land). Trust lands can be alienated or encumbered only by the owner with the approval of the Secretary of the Interior or his/her authorized representative. Trust lands may be located on or off a reservation; however, the Census Bureau tabulates data only for off-reservation trust lands with the off-reservation trust lands always associated with a specific federally recognized reservation and/or tribal government. As for federally recognized reservations, the Census Bureau obtains the boundaries of off-reservation trust lands from American Indian tribal governments through its annual Boundary and Annexation Survey. The Census Bureau recognizes and tabulates data for reservations and off-reservation trust lands because American Indian tribes have primary governmental authority over these lands. The Census Bureau does not identify fee land (or land in fee simple status) or restricted fee lands as specific geographic areas.



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Hawaiian Home Lands

Hawaiian Home Lands (HHLs) are areas held in trust for Native Hawaiians by the state of Hawaii, pursuant to the Hawaiian Homes Commission Act of 1920, as amended. The Census Bureau obtains the names and boundaries for HHLs from state officials. The names of the home lands are based on the traditional ahupua'a names of the Crown and government lands of the Kingdom of Hawaii from which the lands were designated, or from the local name for an area. Being lands held in trust, HHLs are treated as equivalent to off-reservation trust land areas with the American Indian Trust Land/Hawaiian Home Land Indicator coded as "T".



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Oklahoma Tribal Statistical Areas

Oklahoma Tribal Statistical Area (OTSA) Joint-Use Areas, as applied to OTSAs by the Census Bureau, means an area that is administered jointly and/or claimed by two or more American Indian tribes that have a delineated OTSA. The Census Bureau designates statistical joint-use areas as unique geographic entities for the purpose of presenting statistical data. Only Oklahoma tribal statistical areas have statistical joint-use areas.



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State Designated Tribal Statistical Areas

State Designated Tribal Statistical Areas (SDTSAs-referred to as State Designated American Indian Statistical Areas for Census 2000) are statistical entities for state-recognized American Indian tribes that do not have a state-recognized land base (reservation). SDTSAs are identified and delineated for the Census Bureau by a state liaison identified by the governor's office in each state. SDTSAs generally encompass a compact and contiguous area that contains a concentration of people who identify with a state-recognized American Indian tribe and in which there is structured or organized tribal activity. An SDTSA may not be located in more than one state unless the tribe is recognized by both states, and it may not include area within any other American Indian, Alaska Native or Native Hawaiian Area.



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Tribal Designated Statistical Areas

Tribal Designated Statistical Areas (TDSAs) are statistical entities identified and delineated for the Census Bureau by federally recognized American Indian tribes that do not currently have a federally recognized land base (reservation or off-reservation trust land). A TDSA generally encompasses a compact and contiguous area that contains a concentration of individuals who identify with a federally recognized American Indian tribe and in which there is structured or organized tribal activity. A TDSA may be located in more than one state (although none do for 2010), but it may not include area within any other American Indian, Alaska Native or Native Hawaiian area.



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Tribal Subdivisions

American Indian Tribal Subdivisions, described as additions, administrative areas, areas, chapters, communities, county districts, districts, communities, or segments, are legal administrative subdivisions of federally recognized American Indian reservations and off-reservation trust lands or are statistical subdivisions of Oklahoma tribal statistical areas (OTSAs). These entities are internal units of self-government or administration that serve social, cultural, and/or economic purposes for the American Indians on the reservations, off-reservation trust lands, or OTSAs. The Census Bureau obtains the boundary and name information for tribal subdivisions from tribal governments.



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Census Regions and Divisions

Census Divisions

Census Divisions are groupings of states and the District of Columbia that are subdivisions of the four census regions. There are nine census divisions established by the U.S. Census Bureau Puerto Rico and the Island Areas are not part of any census region or census division.



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Census Regions

Census Regions are groupings of states and the District of Columbia that subdivide the United States for the presentation of census data. There are four census regions-Northeast, Midwest, South, and West. Each of the four census regions is divided into two or more census divisions. Puerto Rico and the Island Areas are not part of any census region or census division.



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Census Tracts and Blocks

Census Tracts

Census Tracts are small, relatively permanent statistical subdivisions of a county or equivalent entity that are updated by local participants prior to each decennial census as part of the Census Bureau's Participant Statistical Areas Program. The Census Bureau delineates census tracts in situations where no local participant existed or where state, local, or tribal governments declined to participate. The primary purpose of census tracts is to provide a stable set of geographic units for the presentation of statistical data.

Census tracts generally have a population size between 1,200 and 8,000 people with an optimum size of 4,000 people. A census tract usually covers a contiguous area; however the spatial size of census tracts varies widely depending on the density of settlement. Census tract boundaries are delineated with the intention of being maintained over a long time so that statistical comparisons can be made from census to census. Census tracts occasionally are split due to population growth or merged as a result of substantial population decline.

Census tract boundaries generally follow visible and identifiable features. They may follow non-visible legal boundaries, such as minor civil division (MCD) or incorporated place boundaries in some states and situations, to allow for census tract-to-governmental unit relationships where the governmental boundaries tend to remain unchanged between censuses. State and county boundaries always are census tract boundaries in the standard census geographic hierarchy. Tribal census tracts are a unique geographic entity defined within federally recognized American Indian reservations and can cross state and county boundaries. Tribal census tracts may be completely different from the census tracts and block groups defined by state and county.



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Census Block Groups

Block Groups (BGs) are statistical divisions of census tracts, are generally defined to contain between 600 and 3,000 people, and are used to present sample data and control block numbering. A block group consists of clusters of blocks within the same census tract that have the same first digit of their four-digit census block number. For example, blocks 3001, 3002, 3003 . . . 3999 in census tract 1210.02 belong to BG 3 in that census tract. Block groups generally contain between 600 and 3,000 people. Most BGs were delineated by local participants in the Census Bureau's Participant Statistical Areas Program. The Census Bureau delineated BGs only where a local or tribal government declined to participate and a regional organization or State Data Center was not available to participate.

A BG usually covers a contiguous area. Each census tract contains at least one BG and BGs are uniquely numbered within census tract. Within the standard census geographic hierarchy, BGs never cross county or census tract boundaries but may cross the boundaries of areas any other geographic entity. Tribal census tracts and tribal BGs are separate and unique geographic areas defined within federally recognized American Indian reservations and can cross state and county boundaries. The tribal census tracts and tribal block groups may be completely different from the census tracts and block groups defined by state and county.



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Census Blocks

Blocks (Census Blocks) are statistical areas bounded by visible features, such as streets, roads, streams, and railroad tracks, and by non-visible boundaries, such as selected property lines and city, township, school district, and county limits, and short line-of-sight extensions of streets and roads. Generally, census blocks are small in area; for example, a block in a city bounded on all sides by streets. Census blocks in suburban and rural areas may be large, irregular, and bounded by a variety of features, such as roads, streams, and/or transmission line rights-of-way. In remote areas, census blocks may encompass hundreds of square miles. Census blocks cover the entire territory of the United States, Puerto Rico, and the Island Areas. Census blocks nest within all other tabulated census geographic entities and are the basis for all tabulated data.



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Hydrography

Areal Hydrography

Areal Hydrography consists of both perennial and intermittent area hydrography features, including ponds, lakes, oceans, swamps, and the area covered by large streams represented as double-line drainage.

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Linear Hydrography

Linear Hydrography contains all linear hydrography features with "H" type MTFCC in the MAF/TIGER database. The contents include streams/rivers, braided streams, canals, ditches, artificial paths and aqueducts. A linear hydrography feature may include edges with both perennial and intermittent persistence.

The artificial path features may correspond to those in the USGS National Hydrographic Dataset (NHD). However, in many cases the features do not match NHD equivalent feature and will not carry the NHD metadata codes.

Single-line drainage water features include artificial path features that run through double-line drainage features such as rivers and streams, and serve as a linear representation of these features. Shorelines for area hydrography can be found in the All Lines shapefiles with MTFCC set to either “P0002” (shoreline of perennial water feature) or “P0003” (shoreline of intermittent water feature).


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Glaciers

Glaciers are stored in MAF/TIGER with the MTFCC of H2081.

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Legislative Areas

Congressional Districts

Congressional Districts are the 435 areas from which people are elected to the U.S. House of Representatives. After the apportionment of congressional seats among the states based on decennial census population counts, each state with multiple seats is responsible for establishing congressional districts for the purpose of electing representatives. Each congressional district is to be as equal in population to all other congressional districts in a state as practicable. For the District of Columbia, Puerto Rico, and the Island Areas, a separate code is used to identify the entire areas of these state-equivalent entities as having a single nonvoting delegate.



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State Legislative Districts - Lower

State Legislative Districts (SLDs) are the areas from which members are elected to state legislatures. The Census Bureau first reported data for SLDs as part of the 2000 Public Law 94-171 Redistricting Data File.

The SLDs embody the upper (senateSLDU) and lower (houseSLDL) chambers of the state legislature. Nebraska has a unicameral legislature and the District of Columbia has a single council, both of which the Census Bureau treats as upper-chamber legislative areas for the purpose of data presentation; there are no data by SLDL for either Nebraska or the District of Columbia. A unique three-character census code, identified by state participants, is assigned to each SLD within a state. In Connecticut, Hawaii, Illinois, Louisiana, Maine, Massachusetts, New Jersey, Ohio, and Puerto Rico, state officials did not define the SLDs to cover all of the state or state equivalent area. In these areas with no SLDs defined, the code ZZZ has been assigned, which is treated within state as a single SLD for purposes of data presentation. Maryland also has areas with no SLDs defined; in Maryland these areas are coded with an initial Z by county or equivalent and treated as a unique SLD by county or equivalent.



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State Legislative Districts - Upper

The SLDs embody the upper (senate—SLDU) and lower (house—SLDL) chambers of the state legislature. Nebraska has a unicameral legislature and the District of Columbia has a single council, both of which the Census Bureau treats as upper-chamber legislative areas for the purpose of data presentation; there are no data by SLDL for either Nebraska or the District of Columbia. A unique three-character census code, identified by state participants, is assigned to each SLD within a state. In Connecticut, Hawaii, Illinois, Louisiana, Maine, Massachusetts, New Jersey, Ohio, and Puerto Rico, state officials did not define the SLDs to cover all of the state or state equivalent area. In these areas with no SLDs defined, the code ‘‘ZZZ’’ has been assigned, which is treated within state as a single SLD for purposes of data presentation. Maryland also has areas with no SLDs defined; in Maryland these areas are coded with an initial Z by county or equivalent and treated as a unique SLD by county or equivalent.



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Voting Districts

Voting Districts (VTDs) refer to the generic name for geographic entities such as precincts, wards, and election districts established by state governments for the purpose of conducting elections. States participating in the 2010 Census Redistricting Data Program provided the Census Bureau with boundaries, codes, and names for their VTDs. Each VTD is identified by a one-to six-character alphanumeric census code that is unique within county. The code ‘‘ZZZZZZ’’ identifies a portion of counties (usually bodies of water) for which no VTDs were identified. For 2010 Census, only Kentucky and Rhode Island did not participate in Phase 2 (the Voting District Project) of the 2010 Census Redistricting Data Program and no VTDs exist in these states for 2010 Census data products. In two other states—Montana and Oregon—not all counties have voting districts defined. Participating states often submitted VTDs conforming to the feature network in the MAF/TIGER database rather than the complete legal boundary of the VTD. If requested by the participating state, the Census Bureau identified the VTDs that represent an actual voting district with an ‘‘A’’ in the voting district indicator field. Where a participating state indicated that the VTD has been modified to follow existing features, the VTD is a pseudo-VTD, and the voting district indicator contains ‘‘P.’’ Where a participating state did not indicate to the Census Bureau whether the VTD followed the actual boundaries of the VTD or is a pseudo-VTD, the field is blank. VTD delineation was not offered to the Island Areas.



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Metropolitan and Micropolitan Statistical Areas and Related Statistical Areas

Combined New England City and Town Areas

Combined New England City and Town Areas (Combined NECTAs) consist of two or more adjacent New England city and town areas (NECTAs) that have substantial employment interchange. The NECTAs that combine to create a Combined NECTA retain separate identities within the larger Combined NECTA. Because Combined NECTAs represent groupings of NECTAs they should not be ranked or compared with individual NECTAs.



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Combined Statistical Areas

Combined Statistical Areas (CSAs) consist of two or more adjacent CBSAs that have substantial employment interchange. The CBSAs that combine to create a CSA retain separate identities within the larger CSA. Because CSAs represent groupings of metropolitan and/or micropolitan statistical areas, they should not be ranked or compared with individual metropolitan and micropolitan statistical areas.



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Metropolitan Divisions

Metropolitan Divisions are smaller groupings of counties or equivalent entities defined within a metropolitan statistical area containing a single core with a population of at least 2.5 million may be subdivided to form smaller groupings of counties or equivalent entities referred to as metropolitan divisions. Not all metropolitan statistical areas with urbanized areas of this size will contain metropolitan divisions. A metropolitan division consists of one or more main/secondary counties that represent an employment center or centers, plus adjacent counties associated with the main/secondary county or counties through commuting ties. Because metropolitan divisions represent subdivisions of larger metropolitan statistical areas, it is not appropriate to rank or compare metropolitan divisions with metropolitan and micropolitan statistical areas. It would be appropriate to rank and compare metropolitan divisions.



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Metropolitan New England City and Town Areas

New England City and Town Areas (NECTAs) are an alternative set of geographic entities, similar in concept to the county-based CBSAs defined nationwide, that OMB defines in New England based on county subdivisions-usually cities and towns. NECTAs are defined using the same criteria as county -based CBSAs, and similar to CBSAs, NECTAs are categorized as metropolitan or micropolitan.

Metropolitan NECTAs are designated if the area is associated with at least one urbanized area that has a population of at least 50,000 otherwise the area is designated as micropolitan.



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Metropolitan Statistical Areas

Metropolitan Statistical Areas are CBSAs associated with at least one urbanized area that has a population of at least 50,000. The metropolitan statistical area comprises the central county or counties or equivalent entities containing the core, plus adjacent outlying counties having a high degree of social and economic integration with the central county or counties as measured through commuting.



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Micropolitan New England City and Town Areas

New England City and Town Areas (NECTAs) are an alternative set of geographic entities, similar in concept to the county-based CBSAs defined nationwide, that OMB defines in New England based on county subdivisions-usually cities and towns. NECTAs are defined using the same criteria as county -based CBSAs, and similar to CBSAs, NECTAs are categorized as metropolitan or micropolitan.

Metropolitan NECTAs are designated if the area is associated with at least one urbanized area that has a population of at least 50,000 otherwise the area is designated as micropolitan.



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Micropolitan Statistical Areas

Micropolitan Statistical Areas are CBSAs associated with at least one urban cluster that has a population of at least 10,000, but less than 50,000. The micropolitan statistical area comprises the central county or counties or equivalent entities containing the core, plus adjacent outlying counties having a high degree of social and economic integration with the central county or counties as measured through commuting.



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New England City and Town Area Divisions

New England City and Town Area (NECTA) Divisions: A NECTA containing a single core with a population of at least 2.5 million may be subdivided to form smaller groupings of cities and towns, referred to as NECTA divisions. A NECTA d ivision consists of a main city or town that represents an employment center, plus adjacent cities and towns associated with the main city or town through commuting ties. Each NECTA division must contain a total population of 100,000 or more. Because NECTA divisions represent subdivisions of larger NECTAs, it is not appropriate to rank or compare NECTA Divisions with NECTAs. It would be appropriate to rank and compare NECTA divisions.



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Military and Other Special Land Use Areas


The Census Bureau includes landmarks such as military installations, naional parks, colleges and universities, and correctional facilities in the MAF/TIGER database for locating special features and to help enumerators during field operations. The Census Bureau added landmark features to the database on an as-needed basis and made no attempt to ensure that all instances of a particular feature were included.



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Places and County Subdivisions

Census Designated Places

Census Designated Places (CDPs) are the statistical counterparts of incorporated places and are delineated to provide data for settled concentrations of population that are identifiable by name but are not legally incorporated under the laws of the state in which they are located. The boundaries usually are defined in cooperation with local or tribal officials and generally updated prior to each decennial census. These boundaries, which usually coincide with visible features or the boundary of an adjacent incorporated place or another legal entity boundary, have no legal status, nor do these places have officials elected to serve traditional municipal functions. CDP boundaries may change from one decennial census to the next with changes in the settlement pattern; a CDP with the same name as in an earlier census does not necessarily have the same boundary. CDPs must be contained within a single state and may not extend into an incorporated place. There are no population size requirements for CDPs.

Hawaii is the only state that has no incorporated places recognized by the Census Bureau. All places shown in decennial census data products for Hawaii are CDPs. By agreement with the State of Hawaii, the Census Bureau does not show data separately for the city of Honolulu, which is coextensive with Honolulu County. In Puerto Rico, which also does not have incorporated places, the Census Bureau recognizes only CDPs and refers to them as comunidades or zonas urbanas. Guam also has only CDPs.



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Consolidated Cities

A Consolidated City is a unit of local government for which the functions of an incorporated place and its county or minor civil division (MCD) have merged. This action results in both the primary incorporated place and the county or MCD continuing to exist as legal entities, even though the county or MCD performs few or no governmental functions and has few or no elected officials. Where this occurs, and where one or more other incorporated places in the county or MCD continue to function as separate governments, even though they have been included in the consolidated government, the primary incorporated place is referred to as a consolidated city. The Census Bureau classifies the separately incorporated places within the consolidated city as place entities and creates a separate place (balance) record for the portion of the consolidated city not within any other place.



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County Subdivisions

County Subdivisions are the primary divisions of counties and equivalent entities. They include census county divisions, census subareas, minor civil divisions, and unorganized territories, and can be classified as either legal or statistical. Legal entities are termed minor civil divisions and statistical entities can be either census county divisions, census subareas, or unorganized territories.

Minor Civil Divisions (MCDs) are the primary governmental or administrative divisions of a county in many states (parishes in Louisiana) and of the county equivalents in Puerto Rico and the Island Areas. MCDs in the United States, Puerto Rico, and the Island Areas represent many different kinds of legal entities with a wide variety of governmental and/or administrative functions. MCDs include areas variously designated as barrios, barrios-pueblo, boroughs, charter townships, commissioner districts, election districts, election precincts, gores, grants, locations, magisterial districts, parish governing authority districts, plantations, purchases, reservations, supervisor's districts, towns, and townships. The Census Bureau recognizes MCDs in 29 states, Puerto Rico, and the Island Areas. The District of Columbia has no primary divisions, and is considered equivalent to an MCD for statistical purposes.

In some states, all or some incorporated places are not part of any MCD; these places are termed independent places. In nine states-Maine, Massachusetts, New Hampshire, New Jersey, North Dakota, Pennsylvania, Rhode Island, South Dakota, and Wisconsin-all incorporated places are independent places. In other states, incorporated places are part of, or dependent within, the MCDs in which they are located, or the pattern is mixed-some incorporated places are independent of MCDs and others are included within one or more MCDs.

In New York and Maine, American Indian reservations (AIRs) generally exist outside the jurisdiction of any town (MCD) and thus also serve as the equivalent of MCDs for purposes of data presentation.

In states with legal MCDs, the Census Bureau assigns a default FIPS county subdivision code of 00000 and ANSI code of eight zeroes in some coastal, territorial sea, and Great Lakes water where county subdivisions do not extend into the Great Lakes or out to the three-mile limit.

Census County Divisions (CCDs) are areas delineated by the Census Bureau in cooperation with state, tribal, and local officials for statistical purposes. CCDs have no legal function and are not governmental units. CCD boundaries usually follow visible features and usually coincide with census tract boundaries. The name of each CCD is based on a place, county, or well-known local name that identifies its location.

Census Subareas are statistical subdivisions of boroughs, city and boroughs, municipalities, and census areas, the statistical equivalent entities for counties in Alaska. The state of Alaska and the Census Bureau cooperatively delineate the census subareas to serve as the statistical equivalents of MCDs.

Unorganized Territories (UTs) are defined by the Census Bureau in nine MCD states where portions of counties or equivalent entities are not included in any legally established MCD or incorporated place. The Census Bureau recognizes such separate pieces of territory as one or more separate county subdivisions for census purposes. It assigns each unorganized territory a descriptive name, followed by the designation "UT".



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Estates

Estates are subdivisions of the three major islands in the U.S. Virgin Islands. They primarily represent areas of the former agricultural plantations that existed at the time Denmark transferred the islands to the United States in 1917. The names and boundaries of the estates are in common usage by residents and in government administration. Estates were first recognized as a geographic area for the 2010 Census and are considered their own type of geographic entity separate in the Census Bureau's geographic hierarchy. There are 335 estates.



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Incorporated Places

Incorporated Places are those reported to the Census Bureau as legally in existence as of the latest Boundary and Annexation Survey (BAS), under the laws of their respective states. An incorporated place is established to provide governmental functions for a concentration of people as opposed to a minor civil division, which generally is created to provide services or administer an area without regard, necessarily, to population. Places always are within a single state or equivalent entity, but may extend across county and county subdivision boundaries. An incorporated place usually is a city, town, village, or borough but can have other legal descriptions. For Census Bureau data tabulation and presentation purposes, incorporated places exclude:

1) The boroughs in Alaska (treated as statistical equivalents of counties).

2) Towns in the New England states, New York, and Wisconsin (treated as MCDs).

3) The boroughs in New York (treated as MCDs).



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Subbarrios

Subbarrios are the primary legal subdivisions of the county subdivisions (barrios-pueblo and barrios) in Puerto Rico. Subbarrios divide 31 of the county barrios-pueblo and barrios in 23 of the Puerto Rico county equivalents (termed municipios).



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PUMAs, TADs, TAZs, UGAs and ZCTAs

Public Use Microdata Areas (PUMAs)

Public Use Microdata Areas (PUMAs) are decennial census areas that have been defined for the tabulation and dissemination of Public Use Microdata Sample (PUMS) data, American Community Survey (ACS), and ACS period estimates. For the 2010 Census, the State Data Centers (SDCs) in each state, the District of Columbia, and the Commonwealth of Puerto Rico were given the opportunity to delineate PUMAs within their state or statistically equivalent entity. All PUMAs must nest within states and have a minimum population threshold of 100,000 persons. 2010 PUMAs were built on census tracts, and cover the entirety of the United States, Puerto Rico, Guam and the U.S. Virgin Islands. Because they do not meet the minimum population requirement, the Commonwealth of the Northern Mariana Islands and American Samoa do not contain any 2010 PUMAs.



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Traffice Analysis Districts (TADs)

Traffic Analysis Districts (TADs) are a higher-level geographic entity for traffic analysis. TADs are built by aggregating Traffic Analysis Zones (TAZs), if TAZs also exist for an area. TADs may cross county boundaries, but they must nest within a Metropolitan Planning Organization (MPO). State Departments of Transportation or MPO officials are not required to delineate TADs, but if TADs are delineated for an MPO, all area in that MPO must be assigned to a TAD (there cannot be any gaps in coverage). TADs are required to have a minimum population of 20,000 in order to qualify for three-year sample American Community Survey data.



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Traffice Analysis Zones (TAZs)

Traffic Analysis Zones (TAZs) are special purpose geographic entities delineated by state and local transportation officials for tabulating traffic-related data, especially journey-to-work and place-of-work statistics. TAZs are built from 2010 tabulation blocks. They nest within a county and are delineated on a county basis.



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Urban Growth Areas (UGAs)

Urban growth areas are legally defined entities in Oregon and Washington that the Census Bureau includes in the MAF/TIGER database in agreement with the states. Urban Growth Areas, which are defined around 5-92 incorporated places, are used to regulate urban growth. Urban growth area boundaries, which need not follow visible features, are delineated cooperatively by state and local officials in Oregon and Washington and then confirmed in state law. The Census Bureau collected boundaries for urban growth areas from the State of Oregon as part of a pilot project for Census 2000. The pilot project was extended to the State of Washington for the 2010 Census. Each urban growth area is identified by a 5-digit numeric census code, usually associated with the incorporated place for which the urban growth area is named. There have been updates to the urban growth area where spatial changes may have affected the Census 2000 data in minor instances; however; there have been significant changes to update Oregon and Washington urban growth areas prior to 2010.



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Zip Code Tabulation Area Codes (ZCTAs)

ZIP Code Tabulation Areas (ZCTAs) are approximate area representations of U.S. Postal Service (USPS) five-digit ZIP Code service areas that the Census Bureau creates using whole blocks to present statistical data from censuses and surveys. The Census Bureau defines ZIP Code Tabulation Areas by allocating each block that contains addresses to a single Code Tabulation Areas, usually to the ZCTA that reflects the most frequently occurring ZIP Code for the addresses within that tabulation block. Blocks that do not contain addresses but are completely surrounded by a single Code Tabulation Areas (enclaves) are assigned to the surrounding ZCTA; those surrounded by multiple ZCTAs will be added to a single ZCTA based on limited buffering performed between multiple ZCTAs. The Census Bureau identifies five-digit Code Tabulation Areas using a five-character numeric code that represents the most frequently occurring USPS ZIP Code within that ZCTA, and this code may contain leading zeros.

There are significant changes to the 2010 Code Tabulation Areas delineation from that used in 2000. For 2010 only legitimate five-digit areas are defined so there is no longer full nation-wide coverage. The 2010 ZCTAs will better represent the actual Zip Code service areas because the Census Bureau initiated a process before creation of 2010 blocks to add block boundaries that split polygons with large numbers of addresses using different ZIP Codes.

Data users should not use Code Tabulation Areas to identify the official USPS ZIP Code for mail delivery. The USPS makes periodic changes to ZIP Codes to support more efficient mail delivery. The Code Tabulation Areas process used primarily residential addresses and was biased towards ZIP Codes used for city-style mail delivery, thus there may be ZIP Codes that are primarily nonresidential or boxes only that may not have a corresponding ZCTA.

ZIP Code Tabulation Area Codes—The Census Bureau identifies 5-digit ZCTAs using a five-character numeric code. For ZCTA codes that reflect the 5-digit ZIP Code, the last two characters of the ZCTA code will be numeric. For example, the ZCTA code "00601" represents the 5-digit ZIP Code 00601. The ZCTA delineation process did not recognize ZIP codes ending in "00", such as "29000", as valid 5-digit ZCTA codes.



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School Districts

School Districts are geographic entities within which state, county, or local officials the Bureau of Indian Affairs, or the Department of Defense provide public educational services for the areas residents. The Census Bureau obtains the boundaries, names, local education agency codes, and school district levels for school districts from state and local school officials for the primary purpose of providing the U.S. Department of Education with estimates of the number of children at risk within each school district, county, and state. This information serves as the basis for the Department of Education to determine the annual allocation of Title I funding to states and school districts.

The Census Bureau tabulates data for three types of school districts: elementary, secondary, and unified. Each school district is assigned a five-digit code that is unique within state. School district codes are the local education agency number assigned by the Department of Education and are not necessarily in alphabetical order by school district name.

The elementary school districts provide education to the lower grade/age levels and the secondary school districts provide education to the upper grade/age levels. Unified school districts provide education to children of all school ages in their service areas. In general, where there is a unified school district, no elementary or secondary school district exists, and where there is an elementary school district the secondary school district may or may not exist. In additional to regular school districts, some Census Bureau products contain so-called pseudo school districts described below.

The Census Bureau's representation of school districts in various data products is based both on the grade range that a school district operates and also the grade range for which the school district is financially responsible. For example, a school district is defined as an elementary school district if its operational grade range is less than the full kindergarten through 12 or pre-kindergarten through 12 grade range (for example, K-6 or pre-K-8). These elementary school districts do not provide direct educational services for grades 7-12, 9-12, or similar ranges. Some elementary school districts are financially responsible for the education of all school-aged children within their service areas and rely on other school districts to provide service for those grade ranges that are not operated by these elementary school districts. In these situations, in order to allocate all school-aged children to these school districts the secondary school district code field is blank. For elementary school districts where the operational grade range and financially responsible grade range are the same, the secondary school district code field will contain a secondary school district code. There are no situations where an elementary school district does not exist and a secondary school district exists in Census Bureau records.


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States and Counties

Counties

The primary legal divisions of most states are termed counties. In Louisiana, these divisions are known as parishes. In Alaska, which has no counties, the equivalent entities are the organized boroughs, city and boroughs, municipalities, and census areas; the latter of which are delineated cooperatively for statistical purposes by the State of Alaska and the Census Bureau. In four states (Maryland, Missouri, Nevada, and Virginia), there are one or more incorporated places that are independent of any county organization and thus constitute primary divisions of their states. These incorporated places are known as independent cities and are treated as equivalent entities for purposes of data presentation. The District of Columbia and Guam have no primary divisions, and each area is considered an equivalent entity for purposes of data presentation. All of the counties in Connecticut and Rhode Island and nine counties in Massachusetts were dissolved as functioning governmental entities; however, the Census Bureau continues to present data for these historical entities in order to provide comparable geographic units at the county level of the geographic hierarchy for these states and represents them as nonfunctioning legal entities in data products. The Census Bureau treats the following entities as equivalents of counties for purposes of data presentation: Municipios in Puerto Rico, Districts and Islands in American Samoa, Municipalities in the Commonwealth of the Northern Mariana Islands, and Islands in the U.S. Virgin Islands.



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States

States and Equivalent Entities are the primary governmental divisions of the United States. In addition to the 50 states, the Census Bureau treats the District of Columbia, Puerto Rico, American Samoa, the Commonwealth of the Northern Mariana Islands, Guam, and the U.S. Virgin Islands as the statistical equivalents of states for the purpose of data presentation.



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Transportation

Primary Roads

Primary roads are generally divided, limited-access highways within the Federal interstate highway system or under state management. These highways are distinguished by the presence of interchanges and are accessible by ramps, and may include some toll highways. The Primary Roads shapefile contains all linear street features with MTFCC of S1100.



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Secondary Roads

Secondary roads are main arteries, usually in the U.S. Highway, State Highway, or County Highway system. These roads have one or more lanes of traffic in each direction, may or may not be divided, and usually have at-grade intersections with many other roads and driveways. They often have both a local name and a route number.


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Local Roads

Local Roads include roads that have the following MTFCCs:


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Railroads

Railroad includes spur lines, rail yards, mass transit rail lines such as carlines, streetcar tracks, monorail or other mass transit rail, and special purpose rail lines such as cog rail lines, incline rail lines and trams.


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Tribal Census Tracts and Block Groups

Tribal Block Groups

Tribal block groups are statistical areas defined to provide statistically significant sample data for small areas within American Indian areas, particularly those American Indian areas that crossed state or county boundaries where these boundaries were not meaningful for statistical purposes. The 2010 tribal block groups are defined independently of the standard county-based block group delineation. For federally recognized American Indian tribes with reservations or off-reservation trust land and a population less than 1,200, a single tribal block group is defined. Tribal participants in qualifying areas with a population greater than 1,200 could define additional block groups within their reservation and/or off-reservation trust land without regard to the standard block group configuration.

Tribal block groups nest within tribal census tract.



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Tribal Census Tracts

Tribal census tracts are statistical areas defined within federally recognized American Indian reservations and off-reservation trust land areas. They are designed to be permanent statistical divisions of American Indian areas for the presentation of comparable data between censuses, particularly for those American Indian areas that crossed state or county boundaries where these boundaries were not meaningful for statistical purposes. The 2010 tribal census tracts are defined independently of the standard county-based tract delineation. For federally recognized American Indian tribes with reservations or off-reservation trust land and a population less than 2,400, a single tribal census tract is defined. Qualifying areas with a population greater than 2,400 could define additional tribal census tracts within their area. For 2010, tribal census tracts are defined independently of the standard county-based tract delineation.

Tribal block groups nest within tribal census tract.



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Urban Areas

Urbanized Areas

The Census Bureau's urban-rural classification is fundamentally a classification of areas, identifying individual urban areas and, as a residual, the rural area of the nation. The Census Bureau's urban area definitions represent densely developed territory, encompassing residential, commercial, and other non-residential urban land uses. The Census Bureau defines urban areas after each decennial census by applying specified criteria with decennial census and other data. The Census Bureau classifies as urban all territory, population, and housing units located within urbanized areas (UAs) and urban clusters (UCs), both defined using the same criteria. The Census Bureau delineates UA and UC boundaries to encompass densely settled territory.

Urban Areas (UAs) consist of densely settled territory that contains 50,000 or more people. The Census Bureau delineates UAs to provide a better separation of urban and rural territory, population, and housing in the vicinity of large places.



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Urban Clusters

The Census Bureau’s urban-rural classification is fundamentally a classification of areas, identifying individual urban areas and, as a residual, the rural area of the nation. The Census Bureau’s urban area definitions represent densely developed territory, encompassing residential, commercial, and other non-residential urban land uses. The Census Bureau defines urban areas after each decennial census by applying specified criteria with decennial census and other data. The Census Bureau classifies as urban all territory, population, and housing units located within urbanized areas (UAs) and urban clusters (UCs), both defined using the same criteria. The Census Bureau delineates UA and UC boundaries to encompass densely settled territory.

Urban Clusters (UCs)—An urban cluster consists of densely settled territory that has at least 2,500 people but fewer than 50,000 people. The Census Bureau introduced the UC concept for Census 2000 to provide a more consistent and accurate measure of urban population, housing, and territory throughout the United States, Puerto Rico, and the Island Areas. Prior to Census 2000, urban places of 2,500 or more population were identified outside UAs without regard to population density. In addition, densely settled populations located outside places and outside UAs were classified as rural prior to Census 2000.



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Source: U.S. Census Bureau | Geography Division | geo.tigerweb@census.gov | Last Revised: September 3, 2013